# Project #92586 - Power Confidence and Intervals

PBH592 Quiz: Power and Confidence Intervals Name:

Directions: Before you begin, save this form (FILE, SAVE AS: M6A2_Quiz_Your First and Last Name). Read scenarios 1-3, and answer questions 1—20. In order to receive full credit, you must copy and paste a screen captured image of your data output file from the statistical software that was used to compute the answer. To generate a screen capture image, press ALT + Prt Scr. Save your work frequently to your computer. Once you are ready to submit your work, click Browse My Computer and find your file. Once you've located your file click Open and, if successful, the file name will appear under the Attached files heading. Scroll to the bottom of the page, click Submit and you're done. Be sure to check your work and correct any spelling or grammatical errors before you post.

Scenario 1: Red blood cells are still the most widely transfused blood component worldwide. At present, the most widely used protocol for the storage of red blood cells lasts for up to 42 days. A lab technologist is testing a new protocol for red blood cell storage. Typically, 30% of the vials of the blood prepared using the current protocol show visible agglutination (clumping of red blood cells) after 60 days. She selects a random sample of 200 vials prepared with the new process and finds that after 60 days, only 20 vials show signs of agglutination. Does this data allow us to say that the new protocol makes a difference in the proportion of vials that tend to agglutinate within 50 days?

1. What is the null hypothesis equation for this experiment?

2. What proportion of cells show signs of agglutination with the current protocol?

3. What proportion of cells show signs of agglutination with the new protocol?

4. What is the value for N?

5. What statistical test would you use? z-test

1. z-test

2. Chi square X2

3. Relative Risk

4. Odds ratio

1. Based on the statistical test you chose, do you accept or reject the null hypothesis at P=0.05?

2. What is the 95% confidence ratio?  Please paste your data output file in the area below.

1. What is the power for this test? Paste your output file below.

1. How many samples are needed to achieve a power of 0.80?   Please paste your data output file in the area below.

Scenario 2. To determine whether antimicrobial treatment prevent a bacterial infection, scientists conducted a randomized, double-blind, placebo-controlled trial of treatment with 10 day supply of 200-mg/dose of ampicillin in 482 subjects who had a laceration (cut) that required 4 or more sutures (stiches). They followed those subjects at base line, three weeks, and six weeks after exposure. The results are summarized in Table 1.

Table1. Antimicrobial as Treatment to Prevent a Bacterial Infection

 Develop Bacterial Infection Do not Develop Bacterial Infection Prophylactic treatment with ampicillin 10 235 Placebo Control 80 239

1. What is the null hypothesis equation for this experiment?

2. What statistical test would you use?

1. t-test

2. ANOVA

3. Relative Risk

4. POWER

1. Based on the statistical test you chose, do you accept or reject the null hypothesis at P=0.05?

1. What is the 95% confidence interval?

2. What is the power of this test?
(Alpha=0.05, Expected Relative risk=.163, Expected Proportion in unexposed=0.33) Please paste your data output file in the area below.

Scenario 3:

To determine the effectiveness of a new diuretic drug, urine output was measured in 20 men and compared to 20 men that received placebo control. The data are summarized in Table 2 below. The null hypothesis is: H0: μ Placebo = μ  drug.

Table2.  Effectiveness of New Diuretic Drug

 Mean Urine Output(mg/kg/hr) SD Placebo 1.58 0.66 Drug 2.78 0.77

1. What is the null hypothesis equation for this experiment?

2. What statistical test would you use?

1. t-test

2. ANOVA

3. Relative Risk

4. POWER

1. What is the 95% confidence intervals for this 2 sample t-test?

2. Based on the statistical test that you chose, do you accept or reject the null hypothesis at P=0.05? Please paste your data output file in the area below.

1. What is the Power of this test? Please paste your data output file in the area below.

1. How many samples are needed to achieve a power of 0.80?  Please paste your data output file in the area below.

 Subject Mathematics Due By (Pacific Time) 11/13/2015 12:00 am
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